Power operated clamping device

ABSTRACT

A POWER OPERATED CLAMPING DEVICE HAVING A MULTIPLE MOUNTING FACE BASE, A PIVOTALLY MOUNTED CLAMPING ARM CAM ACTUATED TO PROVIDE HIGH PRESSURE CLAMPING AND RAPID WIDE ANGLE OPENING, AND A LOST MOTION IMPACT PRODUCING CONNECTION FOR CLAMP RELEASING ACTUATION.

March 16, 1971 MC H N 3,570,835

POWER OPERATED CLAMPING DEVICE Filed Oct. 8, 1968 2 Sheets-Sheet 1 ATTORNE VS Files; Oct.

A. W. M PHERSON POWER OPERATED CLAMPING DEVICE Z2 'lll 2 Sheets-Sheet 2IN VEN TOR AZfX/M/Df/F 14 A4 P/A'RSO/V ZZ /,MY/

A TTORNEVS United States Patent 3,570,835 POWER OPERATED CLAMPING DEVICEAlexander W. McPherson, Farmington, Mich, assignor to Dover Corporation(De Sta-Co Division) Filed Oct. 8, 1968, Ser. No. 765,802 Int. Cl. 1325b1/18, /04

US. Cl. 269-32 9 Claims ABSTRACT OF THE DISCLOSURE A power operatedclamping device having a multiple mounting face base, a pivotallymounted clamping arm cam actuated to provide high pressure clamping andrapid wide angle opening, and a lost motion impact producing connectionfor clamp releasing actuation.

BACKGROUND OF THE INVENTION There are many uses for power operatedclamps and work holders which are small and compact in size, willprovide a wide jaw opening and enable maximum clamping pressures to beobtained and released quickly. However, this combination is difficult toattain with such devices as they are presently known.

Most hydraulic and air actuated piston cylinder arrangements, which arepreferred for in-plant uses, require oversized piston cylinders toobtain a sufficient pressure build-up for clamping purposes, or toeffect a release of the jaw mechanism, or to enable a work strokecapable of providing a reasonably wide jaw opening. When bell crank orother lever arm arrangements are used, to obtain a greater mechanicaladvantage, there are added parts subject to fatigue and failure and jawopenings are limited and usually provide restricted access.

In all clamping devices, considerations are also necessary as to how tomount the fixture for best use; particularly where there is an angleblock application of the locking arm or jaw member. Friction and wearmust be minimal, bottoming out in the cylinder must be avoided, ruggedconstruction is necessary without appreciable added weight, and asimplicity of design is essential for ease of maintenance and a minimumof service problems.

SUMMARY OF THE INVENTION The present invention relates to power operatedclamps and like devices, for work holding and other purposes, and inparticular to a cam operated mechanism with a Wedge locking feature thathas many advantages.

A piston cylinder member is used to actuate a roller mounted cross-pinwhich extends through a cam slot in an actuating extension arm thatserves as a work clamping member. The reciprocable stroke of thecross-pin causes cam actuation of the clamping member and provides anunusually wide jaw opening for a relatively short work stroke.

The cam slot is so provided as to cause the cross-pin to wedge with alocking angle in the slot near the end of its work stroke and to assureclamping pressure before the final lock-up. The wedge stroke varianceautomatically compensates for wear by allowing an extra travelallowance. A pre-load stop is provided at the extremity of the clampingstroke which enables use of different clamping arms with clampingsurfaces that can be accurately machined to the mounting surfaces of theunit.

Upon release, an initial freedom of travel provided for the actuator,before dislodging the wedged cross-pin, provides a high inertial impactthat facilitates release and a rapid jaw opening.

These and other abjects and advantages obtained in the practice of thisinvention will be best understood and 3,57%,835 Patented Mar. 16, I971appreciated in the detailed description of a working embodiment whichfollows a brief description of the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a poweroperated clamp including the features of this invention and havingcertain parts shown in dotted and phantom outline, as will be describedlater.

FIG. 2 is an enlarged fragmentary plan view of the front end of thepower operated clamp as seen in the plane of line 2-2 in the firstdrawing figure and looking in the direction of the arrows.

FIG. 3 is a front end view of the power operated clamp as seen in theplane of line 33 in FIG. 1.

FIG. 4 is a sectional view of the operating mechanism in the poweroperated clamp as seen in the plane of line 4-4 in FIG. 2.

FIG. 5 is similar to FIG. 4 with parts shown in a different position.

FIG. 6 is a cross-sectional view as seen in the plane of line 6-6 inFIG. 4.

FIG. 7 is a cross-sectional view as seen in the plane of the offset line77 in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION The power operated clamping device10 shown in the drawing figures includes a piston cylinder actuator 12which includes a mounting head 14 and has a clamping jaw or arm member16 pivotally attached to the mounting head as at 18. An actuatingextension 20, which includes a cam slot 22, is used in swinging theclamping arm to and from the solid line clamping position shown in FIG.1 to that of the phantom line release position 16'.

The piston cylinder actuator 12 includes a fluid pres sure chambermember 24 with closures 26 and 28 at opposite ends and suitableconnections (not shown) for fluid pressure application and release. Themounting head 14 is attached to the operative end of the actuator andincludes a through passage 32 for the piston rod 30 that extends fromwithin the cylinder into the mounting head member.

The mounting head 14 is square in cross-section and includes mountingslots 34 across its top and bottom walls, as best seen in FIG. 1.Relatively offset mounting slots 36 are also provided along its oppositesidewalls, as best seen in FIG. 2. These enable a 4-way mounting withoutmodification of the standard mounting hole pattern and eliminates theneed of angle block applications with respect to the clamping face 38 ofthe clamping arm member 16.

The outwardly extending end of the mounting head 14 is slotted, as at40, to receive the actuating extension 20 of the clamping arm 16therewithin, and it is also formed to include a pair of internal rollertracks 42 and 44 which extend the full length of the mounting head oneach side of the slotted access for the clamping arm and back into thethrough passage 32 for the piston rod 30.

The clamping arm 16 is angular in shape with a short leg 46 pivotallyconnected to the mounting head, as best shown in FIG. 7, by a pivot pin48 through a close but not tight fitting bore hole 50 near its terminalend. The ends of the pivot pin extend into recesses in the sides of themounting head, as best shown at 52 and 54, and a similar hex headed endand fastener 56 on opposite ends of the pivot pin enable the arm to bechanged if and when desired.

In this latter respect, although the clamping member 16 is shown asangular, with a depending clamping arm, it may have a different shapefor disposing its clamping arm and work face in another work plane. Forexample, a phantom view of a clamping arm 116 is shown and identified inFIG. 1 in its work holding position, and in its retracted position as at116'.

The actuating extension 20 of the clamping arm 16 (and of clamp arm .116as well as other variations) extends into the slotted opening 40 in themounting head.

The cam slot 22 in the actuating extension of the arm is angular inshape and includes a dog leg opening 58 that extends radially toward thepivotal axis of the arm, but is offset ahead of the radial line, so thatit is more on a tangential line relative to the pivot pin. The other legopening 60 of the cam slot is on a tangential line on the other side ofthe pin and such that it is more axially aligned with the actuatorcylinder, when the arm is in clamping position. The cam slot opening 60is an angular extension of the slot leg 58 and is actually formed toinclude about a ramp angle relative to the axial line of the actuatorstroke so that the lower edge 62 of the opening serves as an inclinedplane for wedge locking purposes.

The clamping arm 16 is operated by the piston cylinder actuator througha yoke 62 fastened to the end of the piston rod and bifurcated toprovide a slot opening 64 in its end receptive of the actuatingextension of the clamping arm and to support a cross pin 66 that extendsthrough the cam slot 22, as best shown in FIGS. 6 and 7. The piston rod30 has its terminal end reduced in crosssection to provide a bearingshoulder 70 that bears against and will push the connecting part forwardin its actuating stroke. A pin 72 is press fitted in the smallerextended end 68, which is received within the slot opening 64 of theconnecting part, at a spaced distance from the end wall of the slot, toprovide shoulder means for a lost motion retracting stroke before theconnecting part is engaged and drawn back to release the clamp.

The cross-pin 66, that is in the cam slot, is provided with rollers 74and 76 at its opposite ends, which are received and guided in the rollertracks 42 and 44 in the mounting head, and laterally disposed ears 78and 80 near the piston rod end of the connecting part, for like guidepurposes in the guideways.

The power operated clamping device is used as follows:

The mounting head 14 provides the means for fastening the unit to asupporting structure, by use of the mounting slots 34 or 36, with theclamping arm 16 positioned for work clamping and holding purposes, as inthe position shown in FIG. 1. Suitable connections (not shown) are madeto the piston cylinder actuator for fiuid pressure control for advancingand retracting the piston rod 30 to perform its intended function.

The operating sequence is best described with reference to theaccompanying drawings from the retracting stroke of the piston rod, toopen the clamp arm, and then back through its actuating stroke andsubsequent release.

Referring to FIGS. 1 and 4, most particularly, as the piston rod 30 isretracted, it moves freely initially and until the shoulder pin 72engages the end wall of the slot 64 in the yoke 62 at which time itpulls the latter back and, in turn, the roller mounted cross-pin 66rearwardly out of the extended end of the cam slot 22. As the cross-pin66 is retracted in the cam slot leg 60 there is a release of clampingpressure and slight opening movement of the clamping arm member.

When the cross-pin 66 enters the slot opening leg 58, the rapid actioncommences which swings the clamping arm up and into its full 120 openposition limited by registration of the yoke 62 with the piston packinggland 63. A sleeve spacer, not shown, may be installed on the piston rod30 between the yoke 62 and gland 63 to limit the retraction stroke ifdesired, as shown in FIG. 5 and in the dotted line position 16 inFIG. 1. The pin bears against the back wall of the slot opening leg 58and moves relatively down into the slot, as it is pulled straight back,and then moves up the same slot wall surface and beyond into theextended slot leg 60, as shown in FIG. 5, where it will hold theclamping arm open in the fully retracted position.

On the forward or actuating stroke of the piston rod 30, the bearingshoulder pushes the yoke 62 forward and advances the roller mountedcross-pin 66 causing it to move relatively down and back up the cam slotleg 58 and to locate the clamping arm in work holding position. As thepin moves into the extended cam slot leg 60 it bears against the slotwall surface 62 which includes an incline, when the clamping face of thearm or jaw member is in work holding position, and it increases theclamping pressure until the actuating force is balanced by the resistantforce built up due to the wedging of the pin against the inclined rampwall of the slot. The final clamping position is reached at or justprior to the prestop position shown in FIG. 4 where further travel islimited by engagement of an arm stop surface with the mounting head at47. This limit stop may be used to facilitate initial set up of theclamp arm and, if desired, to limit the clamping force applied to thework piece.

The 5 ramp portion 60 of the slot provides positive locking angleclamping within 3 of the final positioning of the clamping arm, and witha clamping pressure that is very high because of the gradual ramp angle.

An overtravel extension of the slot 60 with corresponding extra travelallowance in the cylinder also enables the unit to automaticallycompensate for wear.

In releasing the clamping arm 16 the procedure and operational sequenceis as initially described. However, additional note should be made ofthe advantage of the free travel afforded the piston rod actuator in itslost motion connection with the cross-pin actuating part 62. Noappreciable resistance is present in the piston cylinder at the start ofthe retracting stroke of the piston rod 30 since it does not have toinitially overcome the wedge locking force applying full clampingpressure. Accordingly, the inertial resistance is low and a fast flyingstart is obtained in the retraction stroke providing an impact releaseaction. As the piston rod continues its retracting stroke, the holdingforce on the roller mounted cross-pin 66 in the cam slot 22 is relieved,movement of the pin down the ramp surface meets minimum frictionalresistance, and further momentum is built up to lift the clamping armrapidly to its elevated position.

I claim:

1. A work clamping device, comprising; a base having a plurality ofmounting faces, a single fixed pivot on said base, a clamp arm membermounted on said pivot for rotation in a circular are about the pivotaxis and having an actuating extension and an actuating cam slotprovided therein, a linear power means mounted on said base, areciprocable member disposed in said cam slot actuated by said powermeans, guide means in said base for said reciprocable member providing areactive force cooperating with said cam slot for exerting clampingpressure on said arm, said cam slot including two obliquely disposedportions engageable by said reciprocable member adapted to provide saidclamping pressure engagement in the clamping stroke and rapid openingengagement in the retracting stroke.

2. The work clamping device of claim 1, wherein: said power meanscomprises a piston cylinder actuator operatively connected to saidreciprocable member, and said guide means extends parallel to the axisof said cylinder.

3. The work clamping device of claim 2, wherein: said clamping portionof said cam slot is formed with an acute angle inclination relative tosaid guide means to provide high pressure locking engagement.

4. The work clamping device of claim 3, wherein: said base is fixed tothe head of said piston cylinder actuator and slotted for receiving theactuating extension of said arm member in axial alignment with saidactuator, said reciprocable member comprising a roller mounted crosspin, and said guide means being receptive of the roller mounted ends ofsaid cross pin.

5. The work clamping device of claim 1, including: a lost motionconnection between said power means and reciprocable member for impactactuation of the latter in the retracting stroke.

6. A power operated clamping device comprising: a piston cylinderactuator having a mounting head provided on the operative end thereof, asingle fixed pivot on said head, a work holding arm member mounted onsaid pivot for rotation in a circular are about the pivot axis andhaving an actuating extension including a cam slot disposed for pistonactuation, a roller mounted cross pin operatively engaged by saidactuator, extending through said cam slot and guided for reciprocaltravel within said mounting head, said cam slot including two obliquelydisposed portions engageable by said cross pin adapted to provideclamping pressure engagement in the clamping stroke and rapid openingengagement in the retracting stroke said clamping portion of said camslot formed with an acute angle inclination relative to the reciprocaltravel of said roller mounted cross pin to provide high pressure lockingengagement.

7. The power operated clamping device of claim 6, said arm having a stopengagement with said mounting head at the extremity of the clampingstroke.

UNITED STATES PATENTS 2,845,847 8/1958 Blatt 269-32X 3,482,830 ,12/1969Sendoykas 269 32 3,108,794 10/1963 Blatt 269233 FOREIGN PATENTS1,080,424 8/1967 England 269-32 20 ANDREW R. JUHASZ, Primary Examiner D.D. EVENSON, Assistant Examiner US. Cl. X.R.

